Nozzle for delivering liquid/gas mixture

ABSTRACT

A nozzle arrangement comprising a plurality of nozzle assemblies arranged in an axially aligned and spaced apart arrangement, with a gas and/or liquid inspiration zone between the nozzle assemblies. Each nozzle assembly has a flow passage with an expansion zone formed proximate the outlet end thereof, and at least one discontinuity in the expansion zone formed as an annular shoulder followed by a cylindrical portion, which serves to minimize the build up of a liquid film on the inside surface of the flow passage.

TECHNICAL FIELD

The present invention relates to a nozzle for delivering a liquid/gasmixture to, for example, the intake manifold or combustion chamber of aninternal combustion engine. The nozzle may form part of a fuel injectorfor an engine, particularly but not exclusively where the injectorproduces a mixture where a fine mist of fuel droplets are entrained inan airstream prior to being input to a combustion chamber.

Even though the present invention will be described in relation to apreferred application in fuel injectors for internal combustion enginesit will be appreciated that it has applicability to any environmentwhere a liquid droplet/gas mixture is to be delivered such that liquidfilm adherence at a nozzle outlet is to be ameliorated either incontinuous or discontinuous delivery systems.

BACKGROUND ART

It is known to create a liquid/gas mixture by delivering a generallycohesive sheet of liquid into a stream of gas flowing through a passage,with the gas acting to shear liquid droplets away from the sheet ofliquid. Such a liquid/gas mixture has been found to have a significantlysmaller average liquid droplet size than that produced by deliveringliquid under pressure through a restricted nozzle to form a spray asmany commonly available motor vehicle injectors operate. A liquid/gasmixing apparatus which operates by shearing liquid droplets away from asheet of liquid is disclosed in U.S. Pat. No. 5,735,468 and which isincorporated herein by reference.

Due to the very small size of the liquid droplets, the liquid/gasmixture produced by shearing liquid droplets from a sheet of liquidusing a stream of gas can be delivered along a passage beyond the pointat which the liquid is sheared from the sheet, and out through a nozzle.

If a nozzle has a simple continuous expansion zone leading to itsoutlet, it has been found that such a nozzle delivering liquid/gasmixtures tends to adhere liquid to and build up liquid on the insidesurface of the expansion zone, and which liquid is pushed along thepassage and out from the outlet as relatively large droplets as comparedwith the fine mist entrained in the stream of gas flowing into thenozzle.

It would be desirable to eliminate or at least minimize such adherence,build up and delivery of liquid droplets from the nozzle outlet.

The above and other objects and advantages of the present invention areachieved by the provision of a nozzle arrangement for delivering aliquid/gas mixture which comprises a plurality of nozzle assemblies.Each nozzle assembly has a body which includes a flow-through passageleading to an outlet, an expansion zone proximate the outlet, and atleast one discontinuity in the expansion zone formed as a radiallyextending step-wise enlargement followed by a parallel-sided cylindricalportion extending toward the outlet. The discontinuity is adapted toreduce liquid film adherence at the outlet, and the nozzle assembliesare axially aligned and spaced apart by respective gas and/or liquidinspiration zones.

Preferably each discontinuity is substantially of circumferentialextent.

The expansion zone preferably has a plurality of discontinuities.

Preferably, the flow passage also has a restriction or compression zonespaced upstream from the expansion zone. The restriction or compressionzone is preferably a smoothly converging portion of the flow passage,and which leads to a throat portion which is intermediate therestriction zone and the expansion zone.

The flow passage is preferably generally circular in cross-section as iseach expansion zone.

The or each step-wise enlargement in the expansion zone is/arepreferably in the form of a circumferential edge having a firstdiameter, a radially outwardly extending surface which is generallynormal to the central axis of the flow passage, and an axially extendingcylindrical surface having a second diameter which is a predeterminedamount larger than the first diameter, and which leads to the nextadjacent step-wise enlargement or the outlet.

In one specific embodiment, the intermediate throat portion has adiameter of about 4 mm, the axial cylindrical surface of a firststep-wise enlargements has a diameter of about 5 mm, and the axialcylindrical surface of second and third step-wise enlargements havediameters of about 6 mm and 7 mm respectively. The restriction zonepreferably converges from a diameter of about 10 mm to the 4 mm diameterof the throat portion over an axial distance of about 5 mm. Further, thethroat portion preferably extends about 13 mm, the cylindrical surfacesof first and second step-wise enlargements extend about 3 mm in theaxial direction, and the cylindrical surface of a third step-wiseenlargement extends about 4 mm in the axial direction.

The number of nozzle stages separated by inspiration zones can be variedas desired.

In use with embodiments in accord with the disclosure in U.S. Pat. No.5,735,468 I have found that in the environment of internal combustionengines a minimum quantity of pressurised air is required to atomize aliquid fuel to a desired particle size. In one prototype this has beenestablished at less than 1% stoichiometric air at 100 psi. Thatpressurised air is forced through an injector to shear droplets from theconical sheet of fuel with the resultant fuel/air mixture exiting via adelivery nozzle in accord with an embodiment of the present invention.

The addition of premix air which is a minimum quantity of air necessary(when combined with primary air which effects a shearing action of thefuel within the injector body) that facilitates a preparation of a highquality premix for good combustion. The quantity of premix air includingatomizing air is normally approximately 5% of the total required for astoichiometric mixture.

With the further addition of vaporization air (tertiary air) it ispossible to vaporize the fuel and give further premix to enhancecombustion. Vaporization air is understood to mean the minimum quantityof air necessary (when combined with primary and secondary air) tovaporize the fuel and give further premix to enhance combustion. Suchtertiary air can be inspirated into the fuel/air mixture via theinspiration zone or via radially disposed air inlets on a shroudextending past the outlet of the nozzle assemblies. Of course, as statedabove, the number of nozzle assemblies can be varied as desired.

I have found that a multiple nozzle arrangement in accord with thepresent invention not only ameliorates fuel film adherence but alsocreates good mixing and reduces the velocity of and broadens the fuelair mixture allowing entry of further air into the mixture.

A secondary air nozzle can be attached to an inlet manifold of internalcombustion engine or used to entrain other fuels or both fuel and air.

When used in the environment of a pressurized injector of the formdisclosed in U.S. Pat. No. 5,735,468 the efficiency of a nozzle of thepresent invention is not dependent on a negative pressure generated byan engine which can be the case for, say, air-assisted injectors.

BRIEF DESCRIPTION OF DRAWINGS

Preferred forms of the present invention will now be described by way ofexample with reference to the accompanying drawings, in which:

FIG. 1 is a schematic longitudinal sectional view of an embodiment of anozzle assembly to be used in a nozzle arrangement in accord with thepresent invention;

FIG. 2 is a schematic longitudinal section view of the nozzle assemblyof FIG. 1 and a part of a known liquid/gas mixing apparatus;

FIG. 3 is a schematic detailed view of a portion of the nozzle of FIG. 1showing the flow of gas/liquid mixture and action of the gas stream onliquid which has adhered to the surface of the expansion zone;

FIG. 4 is a general arrangement sectional view of an embodiment of aninjector mounted to an embodiment of a two stage nozzle assembly of thepresent invention;

FIG. 5 is a magnified view of a portion of the injector of FIG. 4;

FIG. 6 schematically depicts an injector nozzle arrangement of FIG. 4configured to provide direct injection into an inlet manifold of aninternal combustion engine;

FIG. 7 is a sectional view of the injector and nozzle arrangement ofFIG. 4 mounted on an intake manifold; and

FIG. 8 is a view similar to FIG. 7 but showing the injector and nozzlearrangement mounted on an intake manifold in an alternative to that ofFIG. 7.

BEST MODE

The drawings show an elongate nozzle 10 with a centrally extendingthrough passage 11, a restriction or compression zone 12 at an inlet end13 and an expansion zone 14 proximate an outlet 15.

The expansion zone 14 is in the form of a series of three step-wiseenlargements 16 each of which define circumferential discontinuitiesalong the flow passage 11. Each step-wise enlargement 16 has acircumferential edge 17, a radially outwardly extending surface 18 whichis generally normal to the central axis of the nozzle 10, and an axiallyextending cylindrical surface 19 having a diameter which is apredetermined amount larger than that of its associated edge 17.

The restriction zone 12 has a conical surface 20 which converges to thediameter of a throat portion 21 which is intermediate the restrictionzone 12 and the expansion zone 14.

Referring to FIG. 2, which shows the nozzle 10 mounted in a part 30 of aliquid/gas mixing apparatus which is generally as disclosed in U.S. Pat.No. 5,735,468 to the present applicant. The mixing apparatus includes aliquid valve 31 which intermittently delivers a radially or conicallyoutwardly projecting sheet of liquid into an annular flow passage 32.The mixing apparatus 30 has gas valving (not shown) which delivers a gasstream through the passage 32 at least from a time just prior to theliquid valve 31 being opened and at least to a time just after theliquid valve 31 is closed. The stream of gas through the passage 32 actsto shear liquid particles away from the sheet of liquid producing a finemist of liquid particles entrained in the stream of gas.

The liquid/gas mixture flows through the passage 32 of the mixingapparatus 30. The passage 32 communicates with the flow passage 11 ofthe nozzle 10 which is positioned downstream of the point at which theliquid particles are sheared away from the liquid sheet. The nozzle 10defines the outlet for the mixing apparatus 30 for delivering theliquid/gas mixture which may be a fuel/air mixture into the combustionchamber of an internal combustion engine (not shown).

In use, the liquid/gas mixture enters the nozzle 10 and is compressedthrough the restriction zone 12 before passing into the intermediatethroat portion 21. This serves to accelerate the stream of gas andliquid particles. When the stream reaches the expansion zone 14, theliquid/gas mixture expands as it passes each of the edges 17 and isthereafter delivered through the outlet 15.

When liquid droplets that have adhered to the flow passage reach thefirst edge 17, it is believed that the action of the gas stream passingover the discontinuity causes the accumulated liquid to be drawn offfrom the surface as relatively small particles, that is, having aparticle size which is considerably smaller than if the accumulatedliquid had been allowed to discharge from the nozzle expansion zonewithout such discontinuities.

More particularly, the discontinuities defined by the step-wiseenlargements 16 cause the stream of gas (with entrained liquid droplets)to flow and expand radially outwardly over and around the edges 17producing turbulence adjacent the radially projecting surface 18.

It has been observed that the nozzle 10 of the embodiment of FIGS. 1-3removes adhered liquid from the expansion zone before it is deliveredthrough the outlet 15 as undesirably large liquid droplets which aregenerally not able to be burnt efficiently in a normal combustion cycle.This benefit is achieved whether the liquid valve 31 and gas valve (notshown) of the mixing apparatus 30 are opened/closed intermittently toproduce intermittent bursts of liquid/gas mixture, or are kept open soas to deliver a continuous stream of the liquid/gas mixture.

In the general arrangement view of the embodiment of FIG. 4 there isshown an injector and nozzle combination 40 comprising a solenoidactuated injector 41 fitted with a two stage nozzle arrangementcomprising atomizer nozzle 49 and mixing nozzle 50.

Injector 41 comprises a solenoid cover 42 which houses a solenoid slug43 and shuttle retainer 44.

Solenoid control needle 45 is housed within needle guide 46 which isdisposed within injector body 47. Needle seat 48 is interposed betweenneedle 45 and atomizer nozzle 49 which directs liquid/gas mixture intoair mixing nozzle 50. Between atomizer nozzle 49 and air mixing nozzle50 there are disposed a plurality of radially extending inspirationpassageways 51 while about shroud 52 there are disposed a plurality oftertiary air inspiration passages 53 downstream from the outlet of airmixing nozzle 50.

In the embodiment of FIG. 4 it has been found that of the order of 1%stoichiometric air at 100 psi coupled to air inlet 54 has beensufficient to shear fuel droplets from a conical sheet of fuel, whichfuel is fed via fuel inlet 55.

To better appreciate the functioning of the airflow and needle movementreference should be made to FIG. 5 which depicts circumferential gap 56between needle 45 and the bore within injector body 41 to permit thepassage of high pressure gas past a conical spray of liquid which formsupon movement of needle 45 away from seat 48. After liquid has beensheared from the conical sheet it passes along passage 56 then through aplurality of circularly disposed passageways 57 which feed into atomizernozzle 49 then through the secondary air inspiration zone defined bypassages 51 before entering air mixing nozzle 50.

FIG. 6 shows an injector and nozzle arrangement of FIG. 4 mounted abovean inlet manifold venturi 60.

Another potential installation arrangement is shown in FIG. 7 where theembodiment of FIG. 4 is mounted to a naturally aspirated or superchargedair inlet manifold 70 with an air bleed passageway 71 feeding inletmanifold air to provide secondary air between nozzles 49 and 50.

FIG. 8 shows yet another mounting arrangement for a naturally aspiratedor supercharged air inlet manifold 80 where the injector body 41 ismounted to manifold 80 with manifold air directly feeding into passages51 rather than by a bypass arrangement as in FIG. 7.

While the nozzles of the depicted embodiments have been described inconjunction with mixing apparatus, it will be appreciated that eachnozzle may be used in single or multi-stage form in any applicationwhere a liquid/gas mixture is to be delivered subject to any relevantdesign criteria.

It will be appreciated by persons skilled in the art that numerousvariations and/or modifications may be made to the invention as shown inthe specific embodiments without departing from the spirit or scope ofthe invention as broadly described. The present embodiments are,therefore, to be considered in all respects as illustrative and notrestrictive.

I claim:
 1. A nozzle arrangement for delivering a liquid/gas mixturecomprising a plurality of nozzle assemblies, each nozzle assemblycomprising;a body having a flow through passage leading to an outlet; anexpansion zone proximate the outlet, and at least one discontinuity inthe expansion zone formed as a radially extending step-wise enlargementfollowed by a parallel-sided cylindrical portion extending toward theoutlet, said discontinuity being adapted to reduce liquid film adherenceat the outlet, and wherein the nozzle assemblies are axially aligned andspaced apart by respective gas and/or liquid inspiration zones.
 2. Anozzle arrangement as claimed in claim 1 wherein the at least onediscontinuity is of substantially circumferential extent.
 3. A nozzlearrangement as claimed in claim 1 wherein there are a plurality ofdiscontinuities in the expansion zone of each nozzle assembly.
 4. Anozzle arrangement as claimed in claim 1 wherein the flow throughpassage has a restriction zone upstream of the expansion zone.
 5. Anozzle arrangement as claimed in claim 4 wherein the restriction zone isa smoothly contracting portion of the flow passage which leads to athroat portion between the restriction and expansion zones.
 6. A nozzlearrangement as claimed in claim 1 wherein the flow through passage is ofa generally circular cross-sectional shape.
 7. A nozzle arrangement asclaimed in claim 1 wherein the outlet of a final downstream nozzleassembly is surrounded by a downstream extending shroud, and whereinsaid shroud comprises an inspiration zone for a gas and/or a liquid tobe added to the liquid/gas mixture downstream of said outlet.
 8. Anozzle arrangement for delivering a liquid/gas mixture comprisinganinjector for forming a pressurized liquid/gas atomized mixture anddelivering the same to an outlet thereof, a plurality of nozzleassemblies, with each nozzle assembly comprising a body having a flowpassage extending axially therethrough from an inlet end to an outletend, an expansion zone formed in the flow passage proximate the outletend thereof, and at least one discontinuity in the expansion zone formedas a radially extending step-wise annular shoulder followed by acylindrical portion; and said nozzle assemblies being disposed in anaxially spaced apart arrangement defining gas and/or liquid inspirationzones between each assembly and being aligned adjacent the outlet of theinjector, such that the atomized mixture flows serially through the flowpassages of the nozzle assemblies, with the discontinuities of thenozzle assemblies acting to reduce liquid film adherence in the flowpassages of the nozzle assemblies.
 9. A nozzle arrangement as claimed inclaim 8 further comprising a gas or liquid inspiration zone interposedbetween adjacent nozzle assemblies.
 10. A nozzle arrangement as claimedin claim 9 further comprising a downstream extending shroud mounted tothe final downstream nozzle assembly, and wherein the shroud comprisesan inspiration zone for a gas and/or a liquid to be added to theatomized mixture flowing through the nozzle assemblies.
 11. A method ofdelivering a liquid/gas mixture comprising the steps of;adding theliquid to a flow of the gas so that the liquid is substantiallyatomized; feeding the so formed liquid/gas mixture through a flowrestriction to a first expansion zone; expanding the mixture in theexpansion zone through at least one expanding discontinuity in the firstzone to an outlet thereof; adding inspirated liquid and/or gas to theliquid/gas mixture downstream of the outlet of the first expansion zoneand then passing the resulting mixture through at least one furtherexpansion zone having at least one further expanding discontinuitytherein and then delivering the resulting/mixture to an outlet of the atleast one further expansion zone.
 12. A method as claimed in claim 11comprising the further step of adding inspirated gas and/or liquid tothe resulting mixture downstream of the outlet of the at least onefurther expansion zone.